Adrenergic control of renin during dietary sodium deprivation in conscious dogs

These experiments evaluated the contribution of α- and β-adrenergic stimulation to plasma renin activity (PRA) during early and long-term dietary sodium restriction, compared with normal sodium intake. Uninephrectomized conscious dogs with catheters in the aorta, vena cava, and remaining renal artery were studied during normal sodium diet (~70 meq/day), after 2-3 days of low-sodium diet (5-7 meq/day), and after ≥2 wk of low-sodium diet. Direct renal arterial (ira) infusion of phenoxybenzamine plus propranolol decreased PRA by similar proportions (39-48%) during all three states of dietary sodium intake. The PRA achieved after adrenergic blockade remained higher (P < 0.05) during early long-term sodium restriction than during normal sodium intake. The effect on PRA of ira infusion of propranolol alone was not different from that of phenoxybenzamine plus propranolol during normal or low-sodium diet, and the magnitude of decrease in PRA during low-sodium diet was the same whether propranolol (1 μg · kg^-1 · min^-1) was infused ira or intravenously. In summary, β-adrenergic stimulation accounts for similar proportions of PRA during early and long-term dietary sodium restriction and during normal sodium intake. Renal α-adrenoceptors appear to play little or no role in control of PRA under these conditions.